In a multiple-input multiple-output (Multiple-Input Multiple-Output, “MIMO” for short) system, it is assumed that a transmit end has N transmit antennas and a receive end has N receive antennas, and N is an integer greater than 1. In a multipath channel environment, a signal received by a receive end antenna may have been transmitted by different channels, and relevancy between the channels is relatively low. When the transmit end sends N data streams to the receive end, that is, when the N different transmit antennas send different data streams, each receive antenna of the receive end can obtain the N data streams by means of dividing. That is, multiple data stream transmission is implemented. For example, when N is equal to 2, dual data stream transmission is implemented.
When no obstacle exists between the transmit end and the receive end, a signal transmission path between the transmit end and the receive end is a straight-line propagation path without an obstacle. The straight-line propagation path without an obstacle may be referred to as a direct path.
In the MIMO system, when the direct path exists between the transmit end and the receive end, a channel rank decreases because channel relevancy increases, and a problem that multiple data stream transmission is not supported may occur. For example, a receive antenna of the receive end cannot obtain, by means of dividing, the N different data streams sent by the transmit end.
In the prior art, an antenna spacing is designed to meet a fixed relationship between the antenna spacing and a data transmission distance between the transmit end and the receive end, so as to decrease the channel relevancy, thereby implementing multiple data stream transmission. However, the antenna spacing is extremely difficult to design. In addition, the prior art is applicable to a scenario in which relative locations of the transmit end and the receive end are relatively fixed. If a relative movement exists between the transmit end and the receive end, for example, the receive end is a mobile terminal, the problem that multiple data stream transmission is not supported may still occur.
For the foregoing problem, a new signal transmission method needs to be put forward.